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Surgical bleeding after pre-operative unfractionated heparin and low molecular weight heparin for coronary bypass surgery

From the Institutes of Cardiology (GR, RD, PAS, MZ, RDC) and Cardiac Surgery (GDG, AC) at "G. d’Annunzio" University, Chieti, and the Institute of Internal Medicine, Catholic University of the Sacred Heart, Policlinico A. Gemelli, Rome, all in Italy

Correspondence: Raffaele De Caterina, MD, PhD, Institute of Cardiology "G. d’Annunzio" University, Chieti c/o Ospedale S. Camillo de Lellis, via Forlanini, 50 66100 Chieti, Italy. E-mail: rdecater{at}unich.it

Background and Objectives: Since the impairment of platelet function may cause excess peri-operative bleeding, pre-operative discontinuation of aspirin and heparin bridging are common for cardiac surgery. We evaluated the impact of pre-operative administration of enoxaparin and unfractionated heparin (UFH) on coagulation parameters and peri-operative bleeding in patients undergoing elective coronary artery bypass grafting (CABG) surgery after discontinuation of aspirin.

Design and Methods: Forty-three patients with three-vessel coronary artery disease undergoing elective CABG surgery discontinued aspirin and were randomized to receive either UFH 180 UI/Kg x 2/day s.c. or enoxaparin 100 UI/Kg x 2/day s.c. until 12 h before surgery (median pre-operative treatment 8 days, range 6–12 days). Surgery was performed as usual with UFH. Neither UFH nor any low molecular weight heparin was given in the immediate post-operative period. The effects of UFH and enoxaparin were monitored by the activated partial thromboplastin time (aPTT) and the Enox-test (sensitive to factor Xa inhibition) using a Rapidpoint^® Coagulation Analyzer. aPTT and factor Xa activity were also measured by standard methods. Peri-operative bleeding and the nadirs of hemoglobin concentration, hematocrit and platelet count were monitored post-operatively.

Results: Patients in the two groups were similar for number of bypasses, on-pump time, total surgery time, and time from the last heparin administration. Coagulation parameters increased significantly and similarly at 30 min and 6 h with both treatments, but returned within the normal range at 12 h. Hemoglobin, hematocrit and platelet counts significantly decreased to the same extent after CABG and re-normalized at the same time. Transfusional requirements of blood and plasma units were similar in the two groups.

Interpretation and Conclusions: From the kinetics of coagulation parameters and the evaluation of bleeding, enoxaparin is a safe alternative to UFH as a bridging therapy to CABG after discontinuation of aspirin.

Key words: unfractionated heparin, enoxaparin, low molecular weight heparins, bypass surgery, bleeding.